Structural variety in zinc telluro-phosphates: syntheses, crystal structures and characterizations of Sr2Zn3Te2P2O14, Pb2Zn3Te2P2O14 and Ba2Zn2TeP2O11

Abstract

Three new zinc telluro-phosphates, Sr₂Zn₃Te₂P₂O₁₄ (1), Pb₂Zn₃Te₂P₂O₁₄ (2) and Ba₂Zn₂TeP₂O₁₁ (3), were grown by flux method, and their crystal structures were solved by X-ray diffraction method. Although all three crystals crystallize into the same space group P2₁/c with similar chemical compositions, they exhibit different topology structure types. 1 features a two-dimensional layered structure with the connection of TeO₄ and (Zn₃TeP₂O₁₈)¹⁶⁻ 12-membered rings (MRs), which are composed of planar square and tetrahedral configuration ZnO₄ groups, tetrahedral PO₄ and seesaw TeO₄. Due to lone-pair Coulomb repulsion of Pb²⁺, the structure of 2, which is also composed of unbalanced seesaw TeO₄ and ZnO₄ groups and distorted PO₄ tetrahedra, is slightly different from that of its analog 1. Compound 3 exhibits a complicated three-dimensional network with (Zn₂PO₉)⁹⁻ 6-MRs and (Zn₂Te₂O₁₀)⁸⁻ 8-MRs built from distorted tetrahedral ZnO₄ and PO₄ groups and trigonal pyramidal TeO₃ units. According to UV-vis-NIR diffuse reflectance spectra, compounds 1, 2 and 3 are highly transparent in the range of 450 to 2500 nm with a UV cut-off of 275 nm, 330 nm and 278 nm, respectively. In addition, the characterizations, including thermal analyses, XPS measurement and dipole moment calculations, are also reported.